Uganda’s National Agricultural Research Organization (NARO) is using liquid nitrogen to conserve banana cell lines in a pioneering effort that could help researchers striving to combat disease and climate threats.
The science of storing tissues in liquid nitrogen, also commonly applied in medical research, is called cryopreservation. The crops so far conserved using this method include the East Africa cooking banana, also known locally as matooke.
The project — the first of its kind in the country — was started by senior research scientist Dr. Priver Namanya Bwesigye at the National Agricultural Research Laboratories (NARL) at Kawanda (a NARO institute), after she trained in France and Belgium in 2002.
Namanya’s training came from a biotechnology partnership for capacity development between NARO and the International Network for the Improvement of Bananas and Plantain, which has since become Biodiversity International.
NARL-Kawanda is the only lab in the world with capacity to make cell suspensions for matooke bananas.The cryopreservation process involves first looking for banana cells from the banana meristems. Cells are then evaluated to establish if they can produce embryos.
Namanya says the cell line that can form embryos is too precious to keep actively growing in tissue culture where it can be lost to contamination or human error. Once a good cell line has been established, it is placed inside a tank containing the liquid nitrogen for storage at minus 196 degrees Celsius.
Cryopreservation has multiple advantages. It is a safe way to store the cells for a long time, maintenance costs are minimal and since there is no exposure to the outside environment, there is no risk of contamination from bacteria or fungi. Researchers can then recover the cells in viable forms when needed, Namanya explained.
Moreover, the method of storing crops in the liquid nitrogen is not affected by external factors such as climate change or a lack of electricity so long as the liquid nitrogen container is firmly locked to avoid spills. Additionally, cells stored in nitrogen are viable for many years, giving researchers easy access anytime they want to do research like crop breeding.
Namanya said the science of cryopreservation is one of the methods that can store indigenous varieties for current and future breeding programs. Currently, NARO has eight varieties stored at Kawanda, which are accessible for research purposes only.
“They are only for our use,” she said.
Crops can be stored in their natural environments too. Namanya said NARO, in partnership with Biodiversity International, is running an on-site regional conservation germplasm collection of over 500 banana types at Mbarara Zonal Agricultural Research and Development Institute. The varieties comprise local, regional and international collections.
Uganda is the second largest producer of bananas in the world, according to Dr. Jerome Kubiriba, team leader of Uganda’s Banana Research Program. It also leads in personal consumption, with each Ugandan consuming an average 240kg annually. Therefore, protecting Uganda’s banana germplasm is important to the country’s food security.
However, Uganda’s banana crop is currently threatened by various diseases, such as the banana bacteria wilt, a virulent scourge that has decimated farmers’ plantations. Namanya, Kubiriba and other scientists believe that technologies such as cryopreservation can be harnessed to preserve precious crop genetic resources.
Concern about the conservation of local crops was one of the reasons Uganda President Yoweri Museveni cited for deferring the National Biosafety Bill in December 2017 after it had been passed by Parliament. However, genetic engineering and other technologies like cryopreservation could actually support the goal of maintaining crop biodiversity by protecting against threats like diseases and drought.
The other public agency conserving species in liquid nitrogen in Uganda is the National Animal Genetic Resources and Data Bank which has semen, eggs, ova, and embryo under seal.